Device and method for thermally treating semiconductor wafers

ABSTRACT

A device for thermally treating semiconductor wafers having at least one silicon layer to be oxidized and a metal layer, preferably a tungsten layer, which is not to be oxidized. The inventive device comprises the following: at least one radiation source; a treatment chamber receiving the substrate, with at least one wall part located adjacent to the radiation sources and which is substantially transparent for the radiation of said radiation source; and at least one cover plate between the substrate and the wall part of the treatment chamber located adjacent to the radiation sources, the dimensions of said cover plate being selected such that it fully covers the transparent wall part of the treatment chamber in relation to the substrate in order to prevent material, comprising a metal, metal oxide or metal hydroxide such as tungsten, tungsten oxide or tungsten hydroxide, from said substrate from becoming deposited on or evaporating onto the transparent wall part of the treatment chamber.

BACKGROUND OF THE INVENTION

This invention relates to a device and a method for thermally treatingsemiconductor wafers having at least one silicon layer to be oxidizedand a metal layer, preferably a tungsten layer, which is not to beoxidized.

In the semiconductor industry there is increasingly the necessity todesign semiconductor elements which are smaller and more efficient. Anexample of this is the increasing use of tungsten instead of tungstensilicide as a component part of the gate assembly in MOS transistors.The use of tungsten as the gate material is advantageous due to the lowspecific resistance of tungsten compared to tungsten silicide. Thismakes it possible to reduce the resistance of the gate, and this leadsto improved electrical performance of the transistors. Moreover, theheight of a gate stack can be considerably reduced by the use oftungsten in contrast to tungsten silicide, and this leads to asubstantial simplification in the following filling and etch stepsbecause the aspect ratio (ratio of height to the distance of the stack)is smaller.

A gate stack of this type is generally formed on a silicon substrate,whereby first of all a gate oxide layer, a polycrystalline siliconlayer, a tungsten nitride layer, a tungsten layer and a silicon nitridelayer are applied.

Subsequently, for defining individual gate areas, selective etch iscarried out, whereby the cauterized side walls of the gate stack areopen. After the etch there follows a gate stack side wall oxidationwhich serves to mend or heal etch damage and reduce the leakagecurrents. When using a tungsten gate, this process must be selective,i.e. whereas the polycrystalline silicon layer has to be oxidized, thetungsten must not be oxidized because the formation of a high-resistancetungsten oxide prevents the electrical functionality of the gate.

Selective oxidation of this type can be achieved by wet oxidation inhydrogen-rich atmospheres within a fast heating unit or a rapid thermalprocessing (RTP) unit.

An RTP unit which can generally be used here is, for example, shown inDE 44 37 361 going back to the applicant.

With the known RTP unit, the wafer to be treated is received in a quartzchamber and is heated by banks of lamps located above and below thequartz chamber. In so doing, it is known to place a thermally stable andgeometrically similar light-absorbing plate in the quartz chamber, andin such a way that the wafer is heated by a radiative and convectiveenergy coupling between the plate and the wafer, instead of being heateddirectly by the lamps. The advantage of this is that the light-absorbingplate is thermally stable and maintains constant emissivity, by means ofwhich exact temperature control of the semiconductor wafer is possible,even if the emissivity of the semiconductor disc is varied. For detailswith regard to the use of a light-absorbing plate, reference is made toDE 44 37 361 so as to avoid repetitions.

With the process described above for the selective side wall oxidation,there is, however, the problem that compounds containing tungsten, inparticular tungsten oxide, can evaporate from the semiconductor wafer.This type of evaporation of the tungsten oxide or of a metal oxide ormetal hydroxide is deposited on the quartz chamber, is reduced there totungsten or to metal and by partial shading of the radiation from thelamps, affects the temperature distribution over the wafer and/or overthe light-absorbing plate and so also over the wafer. With severalprocesses following on from one another, due to stronger and strongershading processes, substantial changes can be made to the processparameters, such as e.g. the process temperature and the wafertemperature.

The aim of this invention, therefore, is to create a device and a methodfor thermally treating semiconductor wafers, whereby the processconditions which substantially remain the same, make it possible withselective oxidation of a silicon layer to be oxidized and of a metallayer, preferably a tungsten layer, not to be oxidized.

SUMMARY OF THE INVENTION

In accordance with the invention, this problem is solved with a devicefor thermally treating semiconductor wafers having at least one siliconlayer to be oxidized by providing at least one radiation source, atreatment chamber receiving the substrate, with at least one wall partlocated adjacent to the radiation sources and which is substantiallytransparent for the radiation of said radiation source, and at least onecover plate between the substrate and the transparent wall part of thetreatment chamber located adjacent to the radiation sources, thedimensions of the cover plate being such that it fully covers thetransparent wall part of the treatment chamber in relation to thesubstrate in order to prevent material comprising a metal, a metal oxideor a metal hydroxide, such as e.g. tungsten, tungsten oxide or tungstenhydroxide from said substrate from becoming deposited on or evaporatingonto the transparent wall part of the treatment chamber.

Material, which can comprise metals such as e.g. tungsten, whichevaporates from the semiconductor wafer, collects on the cover plate andso prevents it from collecting on the transparent wall part of thetreatment chamber, and this prevents deterioration of the process ratiosover several process cycles.

In accordance with a particularly preferred embodiment of the invention,the cover plate for the radiation of the radiation source issubstantially non-transparent so that material such as e.g. tungsten,tungsten oxide or tungsten hydroxide deposited on the cover plate due tothe optical non-transparency of the plate has no effect upon thetemperature distribution of the wafer. With non-transparent cover platesthere is no direct heating of the wafer via the radiation source, ratherheating is indirect via the cover plate.

In order to be able to remove the cover plate easily, for example forthe purpose of cleaning, the cover plate preferably rests loosely oncorresponding holding elements in the treatment chamber. This isparticularly advantageous with transparent cover plates because the samemust be cleaned frequently of the deposits collecting here from thematerial released from the semiconductor wafer so as to maintainunchanging process conditions. But also with non-transparent coverplates it can be advantageous to carry out regular cleaning of the same,e.g. due to the tungsten collecting here, so as to e.g. minimize anycontamination of the process chamber and so as to guarantee reproducibleprocessing of the semiconductor wafer.

Preferably, a handling device is provided for the automatic removal andinsertion of the cover plate from and into the treatment chamber so asto make it possible, for example, to change plates automatically betweensubsequent treatment processes, and without seriously delayingsubsequent treatment processes because of said change. For this, thehandling device is preferably only in contact with the cover plate on asurface facing away from the substrate, so as to avoid contaminating thehandling device with material released from the semiconductor wafer,such as e.g. with tungsten, tungsten or metal oxide, or tungsten ormetal hydroxide. This is particularly advantageous if the handlingdevice is also used for loading and unloading substrates.

Advantageously, at least one cover plate is provided above and below thesubstrate, i.e. on both sides of the substrate so as to receiveevaporating material such as e.g. tungsten as completely as possible.

In order to set the process parameters appropriately, different coverplates are preferably provided above and below the substrate.

Preferably, the surface of the cover plate facing the substrate iscoated, whereby the coating, on the one hand, may enable good adhesionof the material released from the semiconductor wafer, such as e.g. thetungsten and its compounds, and on the other hand, for example, may bemade from a material which is easy to clean.

With another preferred embodiment of the invention, a light-absorbingplate is provided between the cover plate and the transparent wall partof the treatment chamber which makes possible good light absorption andso also indirect heating of the wafer. The light-absorbing plate can besmall and of a form which substantially corresponds to the geometry ofthe semiconductor wafer, because the light absorbing plate does notserve to catch material evaporating or material released from the wafer,such as e.g. tungsten. With one embodiment of the invention, the coverplate is made from glass, in particular quartz glass, which on the onehand is cheap to produce, and on the other hand is easy to clean, andcan also be easily and cheaply coated with, e.g. a silicon nitride, asilicon oxy-nitride or a silicon oxide layer.

With a particularly preferred embodiment of the invention, a device isprovided for the introduction of a non-watery, i.e. water-free orwater-vapor free, hydrogen-containing process gas into the treatmentchamber because this type of process gas makes selective oxidationpossible, in particular when in addition, during the introduction and/orbefore or after the introduction of the water-free process gas a processgas containing water is introduced.

The object which forms the basis of the invention is also solved by amethod for thermally treating semiconductor wafers having at least onesemiconductor layer to be oxidized, preferably a silicon layer, and ametal layer, e.g. a tungsten layer, not to be oxidized, whereby thesemiconductor wafer is received in a treatment chamber with at least onewall part located adjacent to radiation sources, said wall part beingsubstantially transparent for the radiation of the radiation source, andthe wafer is heated, whereby material emitted or evaporated from thesubstrate comprises a metal, a metal oxide or a metal hydroxide, and thematerial is deposited or adsorbed on at least one cover plate betweenthe wafer and the transparent wall part of the treatment chamber, so asto prevent it from becoming deposited on the transparent wall part ofthe treatment chamber.

With this method, there are the advantages already specified above inconnection with the device.

Preferably, during the thermal treatment, a non-watery,hydrogen-containing process gas is introduced into the treatment chamberso as to make selective oxidation possible.

With a particularly preferred embodiment of the invention, the coverplate is removed from the treatment chamber and cleaned betweensubsequent treatment processes.

In general, the aforementioned method in accordance with the inventionand the device in accordance with the invention are used with:

methods for thermally treating semiconductor substrates with at leastone structure S in a process chamber by means of at least one thermaltreatment cycle, whereby

the structure S has at least two different materials A, B, and at leasta first material A with a first component X of a process gas can form afirst material a which is described by a first equilibrium reactionA+X<=>a+a′, and

the second material B with a second component Y of the process gas canform a second material b which is described by a second equilibriumreaction B+Y<=>b+b′, whereby

a′ and b′ are optional reactants,

and whereby during the thermal treatment, for at least an interval oftime, at least one concentration of a component X, Y of the process gasand at least one further process parameter is chosen in such a way, thatthe equilibrium of the first equilibrium reaction is displaced to thefirst material A and the equilibrium of the second equilibrium reactionis displaced to the second material b.

The semiconductor substrates are preferably semiconductor wafers madefrom silicon or materials containing silicon, which comprise e.g.structures in the form of multi-layered substantially planar elementslocated adjacent to one another, whereby the different materials A and Bcan be in different layers of the elements. These multi-layered planarelements are formed e.g. by gate stack structures, as described above,in which, e.g. the gate is formed from tungsten.

The process chamber is preferably the process chamber of a rapid thermalprocessing unit (RTP unit), but can also be a chamber of another unitfor thermally treating semiconductor substrates.

A thermal treatment cycle should be understood as being the thermalprocessing of the semiconductor substrate, so that the semiconductorsubstrate is subjected to a periodically varying temperature sequence,the temperature/time curve of which has at least one temperature valuewhich is higher than the start and end temperature of the treatmentcycle. Thermal treatment of the semiconductor substrate can extend overseveral treatment cycles following on from one another.

With the gate structures specified at the outset, the first material Ais, e.g. tungsten, and the second material B, e.g. silicon orpoly-silicon, as described in greater detail in application DE 101 20523 going back to the applicant. The first material a is a tungsten oxidecompound which may occur, whereby, in particular, it can also be ahydroxide or a tungsten oxide. The second material b is a silicon oxidecompound or a silicon oxide. With the selective oxidation process, amixture of water-vapor and hydrogen is chosen as the first and secondcomponent X, Y of the process gas, so that the tungsten A is not, or isonly to a small extent oxidized or any tungsten oxide or tungstenhydroxide reduced to tungsten, i.e. the equilibrium of the firstequilibrium reaction is displaced to the first material A, i.e. to thetungsten. The second material B, in a special case poly-silicon, on theother hand, reacts with the special process gas of hydrogen and watervapor to silicon oxide (the second material b) so that the equilibriumof the second equilibrium reaction is displaced to the second materialb, the silicon oxide.

The first material A of the structure S can e.g., as described above,comprise a metal such as e.g. molybdenum, a metal oxide, metal nitrideor a metal silicide or a metal hydroxide, which is e.g. oxidized orfurther oxidized by at least one component X of the process gas, orchemically altered in such a way that a volatile first substance a canform (as is e.g. the case with some metal hydroxide formations, e.g.with tungsten hydroxide), which contaminates the process chamber. Thistype of contamination is to be minimized by apparative and/or proceduralmeasures so as to make such processes accessible to mass production.

The second material B of the structure S can comprise a semiconductorsuch as e.g. Si, a semiconductor oxide such as e.g. SiO and/or SiO₂, asemiconductor nitride such as Si₃N₄, a semiconductor oxy-nitride or asilicide, a glass such as e.g. a BPSG layer or material containingcarbon, which, by means of the thermal treatment transforms into adesired chemical compound b (the second material), or which before thethermal treatment is already in this type of compound b (the secondmaterial), whereby, during the thermal treatment, the equilibrium of thesecond equilibrium reaction is displaced to the second material b.

In general, under the second material b, a change to the physicalproperties of the second material B, should also be understood, as, e.g.is the case when BPSG layers are subjected to thermal treatment, andsaid layers then distribute themselves by flowing evenly over thesemiconductor substrate by means of a change in viscosity.

In FIG. 7 the concentration (or the pressure or partial pressure) ofcomponents X,Y and the ratio of the same to a process parameter,preferably the process temperature and the temperature of thesemiconductor substrate, are schematically illustrated. For bothequilibrium reactions there are four areas I to IV in which theequilibrium of the corresponding reaction is respectively displaced toone side, i.e. to the side of the corresponding products. The lines 1and 2 show the parameter area for which the reaction rates k₁, l₁ forthe forward reaction and the reaction rates k₂, l₂ for the returnreaction lead to an equilibrium condition, so that the concentration ofeach reactant does not change any more over time, because of which theselines are described by the equilibrium constants (which are generallytemperature dependent) of the reactions. It should also be mentionedthat by the reaction, the type of the reaction velocity law is alsodefined, and which e.g. can be from 0-th to an n-th order.

The curve 3 in FIG. 7 schematically shows a concentration/temperaturesequence which, e.g. is similar to that in the sequence described inGerman patent application DE 101 205 23, which goes back to theapplicant, for the case of selective side wall oxidation of a tungstengate stack structure. The advantage of this concentration/temperaturesequence for a hydrogen/water vapor mix is that the depositing oftungsten oxides and tungsten hydroxides is reduced in such a way, thatcontamination of the process chamber only becomes noticeable afterseveral thousand semiconductor substrates, and so the process is overallsuitable for mass production. At point 10 of curve 3, for example, purehydrogen with 0% water-vapor is introduced into the process chamber, andthe semiconductor substrate is heated to a temperature of e.g. 800° C.After that, the concentration of water vapor in the hydrogen isincreased to approx. 10%, while the temperature is held constant for acertain time e.g. 10 secs to 30 secs, by means of which point 12 ofcurve 3 is reached on the phase diagram. Finally, the temperature isincreased again, e.g. to approx. 1050° C., whereby the watervapor/hydrogen concentration is kept constant. This is shown by point 11in curve 3. After a certain dwell time of approx. 10 secs to 60 secs inpoint 11, the temperature is reduced, whereby preferably cooling takesplace in pure hydrogen and at low temperatures (e.g. below 800° C.) innitrogen. This is schematically reproduced by the curve sections 11–13and 13–14. During the heat-up phase of the substrate, i.e. during thecurve lineament 10–12–11 of curve 3, it is ensured by the selection ofthe process management with regard to process gas composition andtemperature of the semiconductor substrate, that the process runs inmetal reduction area II and in the silicon or semiconductor oxidationarea III, so that selective oxidation of the semiconductor, but nooxidation of the metal takes places, but that this is reduced with thepossible presence of a metal oxide layer or a metal hydroxide layer sothat after the process, the metal is in the form of pure metal, also onits surface. During cooling, it is preferred if the oxidizing components(e.g. the water vapor) are removed from the process gas, and the coolingtakes place, e.g. in pure hydrogen, whereby, contrary to therepresentation in FIG. 7, the reduction zone IV of the semiconductorwill generally not be passed through, or will only be passed through fora short time, so that any reduction of the semiconductor oxide (secondmaterial b) does not have a damaging or disadvantageous effect upon thestructure S.

It is another aim of this invention to provide an improved oralternative process management to the process management represented byFIG. 7, and one which could also be used in mass production.

This problem is solved by the fact that at least one concentrationand/or a partial pressure or pressure of at least one component X, Y ofthe process gas is constantly changed as a function of the furtherprocess parameter, e.g. the process temperature or the process time.

This is preferably achieved by at least one gas flow meter beingregulated dependent upon the further process parameter or the gas flowmeter being controlled.

By controlling or regulating the gas flow meter, almost any processcurve, as represented e.g. in the phase diagram shown in FIG. 8, can beachieved. The process curve here can be a closed or an “open” curve,i.e. a process whereby the start and end point of the process are thesame in the parameter range shown, or with an “open” curve, the startand end point are different.

Alternatively or additionally to regulation or control of at least onegas flow meter, the total pressure or a partial pressure can be setwithin the process chamber by means of a pump device.

By regulating or controlling at least one gas flow meter and/or thepressure within the process chamber, active control of the processsequence is possible.

Alternatively, or additionally, “passive” control of the processsequence can also take place, whereby a second process gas with clearlydefined composition is introduced into a volume (e.g. chamber volume)filled with a first process gas. By mixing or exchanging the first andsecond process gas, in a certain way constant change of at least onecomponent of the process gas is achieved. Of course, very tight limitsregarding applicability are set for this passive method.

The applicability limits for the passive method for control of theprocess sequence can be extended by an additional chamber, which ifrequired can be variable with regard to volume, whereby this additionalchamber can also serve as a mixing chamber so as to mix the componentsof the process gas before entering into the process chamber and not forthe first time in the process chamber itself.

In FIG. 8 a closed process curve is shown schematically by means of thecurve 10–11–12–13–10, said curve showing one of the possible alternativeprocesses for the process for selective tungsten gate stack oxidationshown in FIG. 7 in curve 3. By active control or regulation of the watervapor/hydrogen ratio as a function of the process temperature(semiconductor temperature), it is possible to let the waterconcentration rise from e.g. originally 0% in point 10 to e.g. 5% to 50%in point 11. Here, with the selective tungsten gate stack oxidation itmakes sense to keep the water vapor proportion low at first so that thesame does not substantially exceed 5%, and preferably does not exceed 1%in the temperature range from room temperature to approx. 700° C. Byslowly increasing the water concentration in the process gas, it isensured that any metal oxide e.g. tungsten oxide or metal hydroxide,e.g. tungsten hydroxide, which may be present, can be reduced by meansof the hydrogen present as the majority component, because the processruns totally in the metal reduction area II. After the reduction of anycompounds a such as e.g. the metal oxide or metal hydroxide mentioned,the temperature is increased further from point 11 to point 12, wherebythe concentration of the water vapor is chosen so that the process alsoruns in the metal reduction zone II, however so that maximum oxidationof the semiconductor takes place with the highest possible processtemperature, i.e. so that the process curve in the phase diagram near tomaximum temperature runs as close as possible to the equilibrium curve 1between e.g. metal oxidation zone I and metal reduction zone II. Thisguarantees, e.g. the best possible oxide quality of the semiconductoroxide layer formed. For cooling of the semiconductor substrate, thecurve shown in FIG. 7 can be chosen, whereby the water vapor content isset to 0% as quickly as possible, e.g. by means of the aforementionedpassive control of the gas composition. Alternatively, or additionally,by means of active control of the gas composition, the water vaporconcentration can be reduced and so the hydrogen concentration increasedas a function of the falling temperature on the curve section 12–13, sothat the oxide growth or the formation of the second material b isreduced. This has often proved to be advantageous because the quality ofthe second material b, e.g. a semiconductor oxide such as SiO₂ is alsoreduced with the falling temperature, and so reduced formation of thisis desirable. This is achieved by constantly reducing the concentratione.g. of the water vapor. From point 13 the concentration of the processgas components can be controlled or regulated in such a way that thesemiconductor reduction area or area IV is not reached.

In the curve 10–11–12–13–10 shown in FIG. 8, the direction and the curvecan run, also as chosen. Above, clockwise running of the process curvewas described, i.e. so that the concentration of at least the dominantreactive process gas components is greater with increasing temperaturethan is this concentration with decreasing temperature. Dependent uponthe application, a process curve can, however, run anti-clockwise, i.e.so that the concentration of the dominant reactive process gas componentis smaller with increasing temperature than with decreasing temperature.This can be advantageous, e.g. with BPSG Reflow processes, whereby thereactive process gas component here is hydrogen and/or water vapor.

As described above, the process curve can be closed or open, by it canalso, as well as strictly monotonously increasing and strictlymonotonously decreasing areas, only comprise monotonous or strictlymonotonous areas, or consist of such an area, such as e.g. a line.

The process curves, as they were schematically represented in FIGS. 7and 8, represent with a single pass through, a thermal treatment cycle.During thermal treatment of the semiconductor substrate, the processcurves can also pass through the cycle more than once to several times.

Preferably, the time interval in which at least one concentration of thecomponents X, Y of the process gas and at least the further processparameter is chosen so that the equilibrium of the first equilibriumreaction is displaced to the first material A and the equilibrium of thesecond equilibrium reaction displaced to the second material b, chosenwithin a thermal treatment cycle.

The interval of time can, however, also extend over several thermaltreatment cycles. In this case, the first equilibrium reaction cansubstantially take place within a thermal treatment cycle, and thesecond equilibrium reaction substantially within another thermaltreatment cycle.

Preferably, the further process parameter is the process temperatureand/or a temperature of a material A, B and/or of a material a, b of thestructure S. In the case of the aforementioned tungsten gate stack tostructure, the temperature of the semiconductor substrate is preferablychosen.

The further process parameter can also comprise a further gasconcentration of a component of the process gas, the pressure of aprocess gas, a partial pressure of a component of a process gas, amagnetic field of predetermined strength and/or a portion of UV lightwhich acts upon the semiconductor substrate, or a combination of theaforementioned parameters.

The structures S preferably have horizontal layers with at least onematerial A, B, but they can also have vertical layers with at least onematerial A, B or a combination of horizontal and vertical layers of thematerials A, B.

In addition, the materials A, B can be separated by at least onematerial C different to A and B.

With a chemical change to the second material B, the second material bcan form on the second material B, preferably on the surface of thesecond material B, as e.g. is the case with oxidation or nitridation ofsilicon.

The semiconductor substrate is preferably a silicon wafer, a crystallineor amorphously grown or deposited semiconductor layer, a substrate or alayer of a IV—IV semiconductor, a II–VI semiconductor or a III–Vsemiconductor.

As already mentioned in relation to the tungsten gate stack structure,the first material A preferably comprises a metal and the secondmaterial a semiconductor B. In this case, the metal of the firstmaterial A can at least partially be covered by a metal oxide or a metalnitride layer, a metal oxynitride layer or a metal hydroxide layer whichcomprises or forms the first material a and can be formed e.g. by meansof the first equilibrium reaction. The semiconductor of the secondmaterial B can be at least partially covered by an oxide, nitride oroxynitride layer which comprises or forms the second material b and canbe formed e.g. by means of the second equilibrium reaction.

Preferably, the first component X and the second component Y are thesame, or at least comprise one same material, such as e.g. a watervapor/hydrogen mixture.

In the same way, the optional reactants a′, b′ can be the same, or atleast comprise one same material.

For example, the first component X and the second component Y cancomprise water, and the reactands a′, b′ hydrogen, or the first and/orsecond component X, Y can comprise a mixture of water and hydrogen. Inthe same way, the first and/or second component X, Y can comprise amixture of water and oxygen.

The method in accordance with the invention can also be carried out insuch a way that the first and/or second component X, Y comprises a firstmixture of water and hydrogen or a second mixture of water and oxygen,and that during the thermal treatment, the first and/or second componentX, Y from the first mixture is returned or transferred into the secondmixture.

With the method in accordance with the invention a process gas can alsobe used which comprises at least during part of the thermal treatmentammonia NH₃. This can e.g. be advantageous with the selective side walloxidation of a tungsten gate stack structure if the tungsten comprises atungsten nitride layer WN_(x), which restricts oxidation of the tungstenand so also volatilization of the tungsten oxide and any tungstenhydroxide. Any contamination of the chamber can be reduced in this way.The tungsten nitride can be formed in pure ammonia by adding ammonia tothe process gas or by a first process step (i.e. a firsttemperature/time curve by means of which the semiconductor substrate isacted upon), or the structure can already have a metal nitride layer onthe metal surface. The ammonia contained in the process gas maintainsthe protective metal nitride layer at least for a certain time or acertain temperature, and so prevents possible metal oxidation. Fortungsten, in the temperature range of between 800° C. and 1000° C. inpure ammonia, a strong formation of tungsten nitride is seen which has apronounced maximum at approx. 930° C. to 950° C., as shown by FIG. 10,in which the resistance of the layer is correlated with that of thelayer thickness of the tungsten nitride layer, shown as a function ofthe temperature. This maximum can e.g. also be used for the temperaturecalibration of RTP units, in particular in order to co-ordinatedifferent units to a common temperature scale. The layer resistance ofthe tungsten nitride layer, for example, can be determined here as afunction of the process temperature. At approx. 940° C. the layerresistance then has a very pronounced maximum which can serve as thecalibration point for the temperature scale.

The formation of metal nitride is of course strongly dependent upon thefurther composition of the process gas, in particular upon any presenceof oxidizing components such as oxygen or water vapor. With the presenceof approx. 15% water vapor in hydrogen in ammonia-free process gas, forexample from approx. 700° C. any tungsten nitride layer with processtimes of 60 secs is clearly broken down so that oxidation of the metalcan then take place, and so the risk of contaminating the chamberincreases. By adding ammonia to the process gas, the decompositiontemperature of the metal nitride can be increased. In this way, it isnow possible to carry out processes corresponding to the curves10–14–15–12–13–10 or 10–11–16–15–12–13–10 or similar shown in FIG. 9,which are distinguished by the fact that due to a protection layer onthe material A, such as e.g. a metal nitride layer, e.g. a tungstennitride layer, which is formed and/or maintained by means of aprotection layer-forming reactive process gas component, at least onepart of the process can proceed within Zone I in which the firstmaterial a forms—i.e. by means of the maintenance or formation of aprotection layer, the equilibrium line 1 of the first equilibriumreaction can be exceeded in a short time, as shown for both of theaforementioned process managements, for example, between points 14 and15, and 16 and 15. The advantage of this is that, e.g. the oxidation ofthe semiconductor can take place at lower temperatures with higherratios, i.e. e.g. by means of higher water concentrations, by means ofwhich the thermal loading of the structures is reduced.

The principle of using a protection layer or the in situ formation orthe maintenance of a protection layer which covers a material A or B ofthe structure, and by means of a reactive protection layer-formingprocess gas component in large areas of thermal treatment offersprotection against the formation of the first material a in area Iand/or the reduction of the second material b in area IV of the phasediagram, does not only make it possible to extend the process managementin area I which e.g. is a metal oxidation area, but expansion into areaIV of the phase diagram is also possible, which is e.g. the reductionarea of the semiconductor, or better of the semiconductor oxide.

Preferably, at least one of the materials A, B or of the materials a, bcomprises tungsten, molybdenum, platinum, iridium, copper and/or oxides,nitrides and/or hydroxides of the same, such as tungsten oxide, tungstennitride or tungsten hydroxide.

In addition, the thermal treatment of the method in accordance with theinvention is preferably carried out in a process chamber of a rapidthermal processing (RTP) or fast heating unit.

It can be advantageous, as already mentioned, for the process chamber tocomprise at least one covering device between the semiconductorsubstrate and at least one process chamber wall for the at least partialcovering of the process chamber wall.

The introduction of covering devices also has the advantage, similar tothat of the protection layer-forming reactive process gas components,that, as is shown schematically in FIG. 9, the thermal treatment of thesemiconductor substrate can take place at least partially in the metaloxidation area I and/or in the semiconductor reduction area IV, withoutthe process chamber itself becoming contaminated in an inadmissible way.Any metal oxides or metal hydroxides are blocked by the covering device.These can then be changed and cleaned, as already mentioned.

In this way, both by means of the cover plates as well as by means ofthe protection layer-forming reactive process gas components, apossibility is created of carrying out the thermal processing ofstructured semiconductor substrates in such a way that the processsequence with regard to concentration of the process gas and a furtherprocess parameter (preferably of the substrate temperature) intersects aphase limit line (1 or 2 in FIGS. 7 to 9) at least once by means of anequilibrium reaction, whereby in at least one phase, a first material aforms, whereby this can be volatile and can lead to possiblecontamination of the process chamber in the absence of a covering devicesuch as e.g. the described cover plate and/or the protection layerand/or the protection layer-forming reactive process gas component. Byactive regulation or control of at least one component of the processgas, this invention opens up a maximum number of process possibilities.In particular, the applicants are expecting applications in the futurein the areas of transistor production, such as e.g. in the aboveillustrated tungsten gate stack process, in the area of high K and low Kapplications, in the area of the glass reflow processes with selectivereactions, or in the area of the production of capacitors.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the device is described in greater detail withreference to the drawings. In the drawings:

FIG. 1 shows a schematic sectional view through a rapid thermalprocessing unit for semiconductor wafers in accordance with a firstembodiment of this invention;

FIG. 2 shows a schematic sectional view through a rapid thermalprocessing unit for semiconductor wafers in accordance with a secondembodiment of this invention;

FIG. 3 shows a schematic sectional view through a third embodiment of arapid thermal processing unit in accordance with this invention;

FIG. 4 shows a schematic sectional view through a fourth embodiment of arapid thermal processing unit for semiconductor wafers in accordancewith this invention;

FIG. 5 shows a schematic sectional view through a fifth embodiment of arapid thermal processing unit for semiconductor wafers in accordancewith this invention;

FIG. 6 shows a sectional view from above in accordance with line V—V inFIG. 5;

FIG. 7 shows a phase diagram with a schematic process management;

FIG. 8 shows a phase diagram with a schematic process management bymeans of active control or regulation of at least one reactive componentof the process gas;

FIG. 9 shows a phase diagram with a schematic process management bymeans of active control or regulation of at least one reactive componentof the process gas which intersects the phase limits;

FIG. 10 shows the layer resistance of a tungsten nitride layer as afunction of the temperature, whereby in pure ammonia, for 60 secs, a 45nm thick tungsten layer on silicon was processed.

DESCRIPTION OF SPECIFIC EMBODIMENTS

FIG. 1 shows a schematic sectional view through a rapid thermalprocessing unit 1 for thermally treating semiconductor wafers 2 havingat least one silicon layer to be oxidized and a metal layer, preferablya tungsten layer, which is not to be oxidized.

The rapid thermal processing unit 1 has a schematically representedhousing 4 which is divided by upper and lower quartz walls 6, 7 into anupper lamp chamber 9, a lower lamp chamber 10 and a process chamber 11.The housing 4 has a closable opening (not illustrated) in the area ofthe process chamber 11, so as to make it possible to load and unload thesemiconductor 2.

In the upper lamp chamber 9, there are a number of heating lamps 13,arranged parallel to one another, and which can be controlled so as toheat the wafer 2 in a known manner.

In a corresponding manner, in the lower lamp chamber 10 there are anumber of heating lamps 14, arranged parallel to one another, which onceagain can be controlled so as to heat the semiconductor wafer 2 in aknown manner.

In the area of the lamp chambers 9 and 10, the housing 4 has inwardlyfacing reflective surfaces so as to reflect the radiation from the lamps13, 14 to the process chamber 11.

Within the process chamber 11, a first holding device 16 is provided fora cover plate 18. The cover plate 18 is made from a material which isnon-transparent for the radiation from the lamps 13 and 14, and has anoutline shape which corresponds to the wafer 2. However, this coverplate 18 is of such dimensions that it has a greater diameter than thewafer 2 and covers a “visual join” between the wafer 2 and the quartzwall 6.

The holding device 16 for the cover plate 18 consists of several supportelements 20 which extend from the quartz plate 6. The support elements20 have respectively a first leg 22 which extends at right angles fromthe upper quartz plate 6. On the lower open end of the leg 22 there is asecond leg 24 which is at right angles to this and extends to the centerof the chamber, at the open end of which there is yet another third leg26 which extends upwardly. The open end of the leg 26 forms a supportfor the cover plate 18 which lies loosely on top of this. Preferably,three of the holding elements 20 are provided for the cover plate 18 soas to provide a secure three-point support. Moreover, the holdingelements 20 are arranged in such a way that it is possible to simplylift the cover plate 18 and pull it out to the side from thenon-illustrated opening in the housing 4.

Within the process area 11 there is, in addition, a second holdingdevice 26 for a second cover plate 28. The holding device 26 consists ofthree support pins 30 which extend at right angles to the lower quartzplate 7, on which the cover plate lies 28 loosely. So as to hold theplate 28 securely, these can have small indentations into which theholding elements 30 extend, such as, for example, a conical indentationinto which a conical point of the holding element 30 can extend. Thistype of complementary indentation can also be provided for the uppercover plate 18.

On an upper side of the lower cover plate 28 there are a number ofsupport pins 34, preferably three, which extend substantially at rightangles to the cover plate 28 and form a support for the wafer 2. Theupper cover plate 18 and the lower cover plate 28 are respectively madefrom a material which is non-transparent for the radiation from thelamps 13 and 14, so that the wafer 2 which is positioned between theseis not directly heated by the radiation from the lamps 13, 14, ratherindirectly via a radiative and convective energy coupling between thewafer 2 and the cover plates 18, 28, which are heated by the respectivelamps 13 and 14. Alternatively, it is however also possible to designthe cover plates 18, 28 so that they are transparent for the radiationfrom the lamps 13 and 14, so as to make it possible to heat the wafer 2directly by the lamps 13 and 14.

In the following, the treatment of a semiconductor wafer 2 in the rapidthermal processing unit 1 in accordance with the invention is describedin greater detail with reference to FIG. 1.

First of all, a semiconductor wafer 2 with a silicon layer to beoxidized and a metal layer, preferably a tungsten layer, which is not tobe oxidized is loaded into the rapid thermal processing unit 1 and laidonto the support pins 34. Next, the housing 4 is closed, and first ofall nitrogen is conveyed through the process area 11 at a low firsttemperature so as to remove any oxygen which may be present. Purehydrogen gas is then introduced into the process area, whereby thetemperature of the wafer 2 is first of all held constant, and thenincreased to a higher temperature of, for example, 800° C.

After reaching the increased temperature of, for example, 800° C., ahydrogen/water mixture is introduced into the process area, whereby, forexample, an atmosphere with a water content of under 20 volume percent,and in particular 14 volume percent is set. The temperature of the waferis first of all held constant, and then increased to an even highertemperature of for example 1050° C. With this increased temperaturethere is a reaction between the hydrogen/water mixture and the wafer. Inparticular, there is oxidation of the accessible surfaces of the siliconlayer of the semiconductor wafer. Oxidation of the metal or tungstenlayer can be controlled by setting a specific mix ratio of thehydrogen/water mix. In order to prevent oxidation of the metal, the mixratio must be set so that an oxidation reaction of the mixture (causedby oxygen in the water) and an associated reduction reaction (caused bythe hydrogen) remain in equilibrium or the reduction reaction in slightinequilibrium. Meanwhile, there is always the formation of a tungstenoxide which is volatile at the process temperatures, and so candistribute itself in the process area, where it is then reduced by thehydrogen to metallic tungsten. In order to prevent the volatile tungstenoxide from becoming deposited on the process chamber walls, and inparticular on the quartz walls 6, 7, the upper and lower cover plates18, 28 are provided, and these limit the freedom of movement of thevolatile tungsten oxide and offer surfaces for the adsorption of thetungsten oxide or the metallic tungsten. Tungsten oxide evaporating fromthe wafer 2 can adhere to the cover plates 18, 28 and it is preventedfrom moving towards the quartz plates 6, 7 and from contaminating thesein such a way that the heat output from the lamps 13, 14 is affected. Ifthe tungsten oxide deposits itself on the cover plates 18, 28, it isoxidized to tungsten by the hydrogen, as mentioned, and it remains onthe cover plates 18, 28. Because these are non-transparent for theradiation from the lamps 13, 14, the deposits do not affect the heatoutput of the rapid thermal processing unit 1.

After the treatment with the hydrogen/water mixture, there follows a newtreatment with pure hydrogen gas so as to bring about total return ofany tungsten oxide into metallic tungsten, and the temperature withinthe process area 1 is lowered. Next, nitrogen is made to flow throughthe process area once again.

By introducing a non-watery substance containing hydrogen before andafter treating the wafer with a hydrogen/water mixture, the formation oftungsten oxide and the release of the same from the wafer is reduced. Bymeans of the cover plates 18, 28, metallic tungsten or tungsten oxidecan moreover be prevented from being deposited on the quartz plates 6,7.

Next, the wafer is taken out of the rapid thermal processing unit 1, anda new wafer can be installed for a corresponding treatment. After aspecific number of wafer treatments, the cover plates 18, 28 whichrespectively lie loosely on their holding elements, can also be removedfrom the process area so that they can be cleaned, and so as to removeany tungsten which has been deposited on them. The cover plates 18, 28can be removed with the same handling device as the wafer 2, whereby inthis case, the handling device preferably engages the surfaces facingaway from the wafer 2, so as to avoid contamination of the handlingdevice. Alternatively, the handling device can also be cleaned betweenhandling of the covering plates 18, 28 and handling of a wafer 2.

Although the cover plates 18, 28 were described as impermeable to theradiation from the lamps, it is also possible to use transparent plates,whereby these must then be removed more frequently from the processchamber and cleaned, if so required after each time that the wafer ishandled, so as to prevent the influence of metal which has beendeposited onto the cover plates 18, 28. For example, the lower coverplate and the wafer can be removed as one unit from the process chamber.If the upper cover plate were supported by the lower cover plate, bothcover plates could be removed as one unit with the wafer positionedbetween them. Also, a handling device could be provided with threesupport or gripping elements which would mean that the cover plates andthe wafer could be grasped at the same time.

FIG. 2 shows an alternative embodiment of a rapid thermal processingunit 1 of this invention. In so far as the same or similar componentsare present, the same reference numbers as in FIG. 1 will be used.

The rapid thermal processing unit 1 in accordance with FIG. 2 once againhas a housing 4 which is internally divided by quartz walls 6, 7 intoupper and lower lamp chambers 9, 10, and a process chamber 11 locatedbetween the same. On the inside of the process chamber 11 there is onceagain a first holding device 16 provided to hold a cover plate 18,whereby the holding device 16 is of the same structure as with theembodiment in accordance with FIG. 1. In addition, a second holdingdevice 26 is provided to hold a second, lower cover plate 28. Theholding device 26 is once again the same as the holding device inaccordance with FIG. 1. When the process chamber 11 is loaded, asemiconductor wafer 2 is positioned between the cover plates 18, 28, asshown in FIG. 2. The cover plates 18, 28 once again extend parallel tothe wafer 2, and in comparison to the embodiment in accordance with FIG.1, they are located at a smaller distance away in relation to the wafer2. In this way, better screening from evaporating metal or metal oxidecan be achieved for the quartz walls 6, 7. In the embodiment shown inFIG. 2, the cover plates 18, 28 are made from a non-transparentmaterial. Above and below the cover plates 18, 28 non-transparent,light-transforming plates 40, 41 are, however provided for the radiationfrom the lamps 13, 14, and these are held by holding devices (notillustrated in detail) within the process chamber. Thelight-transforming plates 40, 41 are held parallel to the cover plates18, 28 and the wafer 2 which is positioned between the same. Thelight-transforming plates 40, 41 have substantially the same outerdimensions as the wafer 2, so as to substantially prevent radiation fromthe lamps 13, 14 from falling directly onto the wafer 2. Instead ofbeing heated directly by the lamp radiation, there is once againindirect heating of the wafer 2 by means of the light-transformingplates 40, 41. Contrary to the cover plates 18, 28, thelight-transforming plates 40, 41 are substantially fixed in the processchamber 11.

The treatment of a semiconductor wafer in the rapid thermal processingunit 1 in accordance with FIG. 2 happens substantially in the same wayas treatment in the rapid thermal processing unit 1 in accordance withthe first embodiment shown in FIG. 1.

FIG. 3 shows another alternative embodiment of a rapid thermalprocessing unit 1, whereby in FIG. 3 once again the same referencenumbers are used as in FIG. 1, in so far as the same or similar elementsare described.

The rapid thermal processing unit 1 in accordance with FIG. 3 is of thesame structure as the rapid thermal processing unit 1 in accordance withFIG. 1, whereby, however, in addition a compensation ring 46 is providedaround the substrate 2 in order to compensate edge effects when heatingor cooling the semiconductor wafer 2. The compensation ring 46 can be inone section or consist of several segments, and can also be removed fromthe process chamber 11 of the rapid thermal processing unit 1 forcleaning. The compensation ring 46 is held by a holding device (notillustrated in detail) in the plane of the wafer 2, whereby thecompensation ring 46 can be at least partially moved out from the planeof the wafer 2 so as to make loading and unloading of the wafer 2easier. This can be achieved, for example, by swivelling thecompensation ring 46, or certain segments of the same.

The wafer treatment in the rapid thermal processing unit 1 in accordancewith FIG. 3 happens in the same way as with the first embodiment shownin FIG. 1.

FIG. 4 shows another embodiment of a rapid thermal processing unit 1 forsemiconductor wafers 2. In FIG. 4 the same reference numbers are usedonce again as with the previous embodiments, in so far as the same orequivalent components are used.

The embodiment in accordance with FIG. 4 substantially corresponds tothe embodiment in accordance with FIG. 3. Within a process chamber 11,upper and lower cover plates 18, 28 are provided which are held bycorresponding holding devices parallel to a wafer 2 received in theprocess chamber 11.

With the embodiment in accordance with FIG. 4, the upper cover plate 18is made from a material which is non-transparent for the lamp radiation,whereas the lower cover plate 28 is made from a material which issubstantially transparent for the lamp radiation, such as for examplequartz. In order to prevent direct heating of the wafer 2 by the lamps14 located at the bottom, a light-absorbing plate 50 is provided betweenthe lower quartz wall 7 and the cover plate 28 which is substantially ofthe same structure as the light-absorbing plate 41. The light-absorbingplate 50 is held in the process chamber 11 by corresponding holding pins52.

The treatment of the semiconductor wafer 2 in the rapid thermalprocessing unit 1 in accordance with FIG. 4 happens in the same way asthe treatment in the rapid thermal processing unit 1.

FIG. 5 shows another alternative embodiment of the invention, wherebythe rapid thermal processing unit 1 shown in FIG. 5 is of substantiallythe same structure as the rapid thermal processing unit 1 in accordancewith FIG. 1. The only difference is that the semiconductorwafer 2 is notlaid on top of holding pins 34 which extend from the lower cover plate28. Instead, a separate holding device 56 is provided for thesemiconductor wafer 2 which is coupled with the leg 22 of the holdingdevice 16. The holding device 56 has a first leg 58 which extends atright angles to the leg 22 of the first holding device 16, a leg 60which extends at right angles to this and to the center of the chamber,and a leg 62 which extends upwards, the open end of which forms asupport surface for the wafer 2. The advantage of this holding device 56for the wafer 2 is that the lower cover plate has a level surfacewithout holding elements on top of it, and is therefore easier to handleand to clean.

FIG. 6 shows a sectional view through the rapid thermal processing unit1 along the line V—V in FIG. 5. As can be seen in FIG. 6, the holdingdevice 56 has three holding elements, of which in FIG. 6 the respectiveleg 60 can be identified. The holding elements are arranged in such away, however, that the wafer 2 can be removed from the side of theprocess chamber 11 after lifting off from the legs 62, as shown by thearrow A. The special holding device 56 for the wafer 2 thus makes itpossible to freely grasp the wafer 2, and makes it possible to load andunload the same easily. This type of arrangement of the individualholding elements is also provided for the holding elements of theholding device 16 in order to make it possible to remove the upper coverplate 18 from the side.

The treatment of the wafer 2 in the rapid thermal processing unit 1 inaccordance with FIG. 6 happens in the same way as with the firstembodiment shown in FIG. 1.

Although the invention was described using preferred embodiments of theinvention, it is not limited to the embodiments actually described. Forexample, the holding devices 16, 26 and 56 for the cover plates 18, 28and the wafer 2 can extend not only from the respective upper and lowerquartz plates 6,7, but also from side walls of the process chamber 11.Moreover, the quartz walls 6,7 need not extend over the full width ofthe process chamber 11. Rather, they can also form just one section ofthe upper and lower walls of the process chamber 11. In order to makecleaning of the respective cover plates easier, the surfaces facing thesubstrate could respectively be coated, whereby the coating preferablyconsists of a material which is easy to clean. Other preferableembodiments of the invention are described in the patent claims. Thefeatures of the different embodiments and examples can be changed and/orcombined with one another in any way, so long as they are compatible.

The specification incorporates by reference the disclosure of Germanpriority document 102 36 896.1 filed 12 Aug. 2002 and PCT/EP2003/008220filed 25 Jul. 2003.

The present invention is, of course, in no way restricted to thespecific disclosure of the specification and drawings, but alsoencompasses any modifications within the scope of the appended claims.

1. A device for thermally treating semiconductor wafers or substrateshaving at least one silicon layer that is to be oxidized and a metallayer, preferably a tungsten layer, that is not to be oxidized, saiddevice comprising: at least one radiation source; a treatment chamberfor receiving a substrate, wherein said chamber has at least one wallpart located adjacent to the at least one radiation source, and whereinsaid wall part is substantially transparent for radiation from said atleast one radiation source; at least one cover plate disposed betweenthe substrate and said at least one wall part of said treatment chamberlocated adjacent to said at least one radiation source, wherein said atleast one cover plate is dimensioned such that it fully covers saidtransparent wall part of said treatment chamber in relation to thesubstrate, in order to prevent material, comprising a metal, metal oxideor metal hydroxide, such as tungsten, tungsten oxide or tungstenhydroxide, emitted or evaporated from said substrate from reaching saidtransparent wall of said treatment chamber; and a handling device forautomatically removing and inserting said at least one cover plate fromor into said treatment chamber, wherein said handling device contactssaid cover plate only on the surface facing away from the substrate. 2.A device according to claim 1, wherein said at least one cover plate issubstantially non-transparent for the radiation of said at least one ofradiation source, and/or said at least one cover plate lies loosely onholding elements in said treatment chamber.
 3. A device according toclaim 1, wherein said handling device for said at least one cover plateis also provided for a loading and unloading of substrates.
 4. A deviceaccording to claim 1, wherein at least one respective cover plate isdisposed above and below the substrate, and/or wherein different coverplates are provided above and below the substrate.
 5. A device accordingto claim 1, wherein a surface of said at least one cover plate facingthe substrate is coated, for example by a material that is easy toclean.
 6. A device according to claim 1, wherein a light-absorbing plateis disposed between said at least one cover plate and said at least onetransparent wall part of said treatment chamber.
 7. A device accordingto claim 1, wherein said at least one cover plate is composed of glass,in particular quartz glass.
 8. A device according to claim 1, wherein atleast one device is provided for introducing a non-watery, hydrogencontaining process gas into said treatment chamber.
 9. A deviceaccording to claim 8, wherein a control unit is provided for introducingsaid non-watery, hydrogen containing process gas prior to and/or afterintroduction of a hydrogen/water mixture.
 10. A method for thermallytreating semiconductor wafers having at least one semiconductor layerthat is to be oxidized, preferably a silicon layer, and a metal layer,for example a tungsten layer, that is not to be oxidized, wherein asemiconductor wafer is disposed in a treatment chamber having at leastone radiation source and a wall part located adjacent to the radiationsource, said wall part being substantially transparent for radiation ofthe radiation source, said method including the steps of introducing atleast one process gas into said treatment chamber; heating the wafer,wherein material emitted from or evaporating from the wafer comprises ametal, metal hydroxide or metal oxide, and the material is deposited oradsorbed on at least one cover plate disposed between the wafer and thetransparent wall part of the treatment chamber, so as to prevent thematerial from reaching the transparent wall part of said treatmentchamber; and removing the at least one cover plate from the treatmentchamber, using an automatic handling device, after the thermal treatmentof a semiconductor wafer and inserting a cover plate into said treatmentchamber prior to a subsequent thermal treatment of a semiconductorwafer, wherein the handling device contacts the cover plate only on asurface facing away from the wafer.
 11. A method according to claim 10,wherein said at least one cover plate is removed from said treatmentchamber and cleaned between substrate treatments.
 12. A method accordingto claim 10, wherein during the thermal treatment, at least onenon-watery hydrogen containing process gas is introduced into saidtreatment chamber, for example prior to and/or after introduction of amixture of hydrogen and water.
 13. A method according to claim 12,wherein the water content of the hydrogen/water mixture is controlledsuch that oxidation of the metal by the oxygen contained in the water,and a reduction of the resulting metal oxide, is substantially kept inequilibrium by the hydrogen.
 14. A method according to claim 13, whereina proportion of water in the mixture is less than 20%, and in particularabout 14%.
 15. A method for thermally treating semiconductor substrateshaving at least one structure in a process chamber by means of at leastone thermal treatment cycle, wherein the structure has at least twodifferent materials A, B, wherein said material A can form a firstmaterial a having a first component X, wherein such forming is describedby a first equilibrium reactionA+X<=>a+a′; and wherein said material B can form a second material bhaving a second component of a process gas Y, wherein such forming isdescribed by a second equilibrium reactionB+Y<=>b+b′; whereby a′ and b′ are optional reactants, and wherein duringthe thermal treatment, for at least an interval of time, at least oneconcentration of a component of the process gas X and/or Y, and at leasta further process parameter, are chosen such that the first equilibriumreaction is displaced to the first material A and the second equilibriumreaction is displaced to the second material b, and wherein at least oneconcentration and/or a partial pressure of at least one component of theprocess gas X and/or Y is constantly changed as a function of thefurther process parameter.
 16. A method according to claim 15, whereinat least one gas flow meter is regulated or controlled as a function ofthe further process parameter, and/or by means of a pump device, thetotal pressure or a partial pressure within the process chamber is set.17. A method according to claim 15, wherein a second process gas havinga defined composition is introduced into a volume, for example avariable volume, filled with a first process gas.
 18. A method accordingto claim 15, wherein the time interval is within one thermal treatmentcycle, or extends over several thermal treatment cycles.
 19. A methodaccording to claim 15, wherein the first equilibrium reactionsubstantially takes place within one thermal treatment cycle, and thesecond equilibrium reaction substantially takes place within anotherthermal treatment cycle.
 20. A method according to claim 15, wherein thefurther process parameter is the process temperature and/or atemperature of a material a, b of the structure.
 21. A method accordingto claim 15, wherein the further process parameter comprises a furthergas concentration of a component of the process gas, the pressure of theprocess gas, a partial pressure of a component of a process gas, amagnetic field of pre-determined strength, a portion of UV, or thecombination of the aforementioned parameters that act upon thesemiconductor substrates.
 22. A method according to claim 15, whereinthe structure has horizontal layers with at least one material A or B,or the structure has vertical layers with at least one material A, B.23. A method according to claim 15, wherein the materials A, B areseparated by at least one material C that is different from A and B,and/or wherein the second material b forms on the material B.
 24. Amethod according to claim 15, wherein the semiconductor substratecomprises a silicon wafer, a crystalline or amorphously grown ordeposited semiconductor layer, a substrate or a layer of a IV—IVsemiconductor, a II–VI semiconductor, or a III–V semiconductor.
 25. Amethod according to claim 15, wherein the first material A comprises ametal, and the second material comprises a semiconductor B.
 26. A methodaccording to claim 25, wherein the metal of the first material A iscovered by a metal oxide or metal nitride layer that comprises or formsthe first material a and that can be formed, for example, by means of anequilibrium reaction.
 27. A method according to claim 25, wherein thesemiconductor of the second material B is at least partially covered byan oxide, nitride or oxi-nitride layer that comprises or forms thesecond material b, and that can be formed, for example by means of asecond equilibrium reaction.
 28. A method according to claim 15, whereinthe first component X or the second component Y are the same or they atleast comprise a same material, and/or wherein the optional reactantsa′, b′ are the same or at least comprise the same material and/orwherein the first component X and the second component Y comprise waterand/or wherein the reactants a′, b′ comprise hydrogen, and/or whereinthe first and/or second component X, Y comprises a mixture of water andhydrogen or a mixture of water and oxygen.
 29. A method according toclaim 15, wherein the first and/or second component X, Y comprises afirst mixture of water and hydrogen or a second mixture of water andoxygen, and wherein during the thermal treatment, the first and/or thesecond component X, Y is transferred from the first mixture into thesecond mixture, or vice versa.
 30. A method according to claim 15,wherein at least the material A and/or the second material b comprises aprotection layer that is formed and/or maintained by means of aprotection layer-forming reactive process gas component during thethermal treatment, and wherein said protection layer makes it possible,at least for a short time, to process the semiconductor substrate inparameter areas with regard to the concentration of the process gasesand at least one further parameter, preferably the temperature of thesemiconductor substrate, In which the equilibrium reaction is displacedto the first material a and/or to the second material B.
 31. A methodaccording to claim 30, wherein the process gas comprises ammonia, atleast during part of the thermal treatment, and/or wherein theprotection-layer-forming reactive process gas component comprisesammonia.
 32. A method according to claim 15, wherein at least one of thematerials A, B or the materials a, b comprises tungsten, molybdenum,platinum, iridium, copper and/or the oxides or nitrides thereof, such astungsten oxide and/or tungsten nitride.
 33. A method according to claim15, wherein the thermal treatment is carried out in a process chamber ofa rapid thermal processing unit, which is, for example,temperature-calibrated in a temperature range of between 930 and 950°C., with the temperature calibration making use of the layer grown froma tungsten nitride layer in ammonia.
 34. A method according to claim 15,wherein the process chamber comprises at least one covering devicedisposed between the semiconductor substrate and at least one processchamber wall for at least partially covering the process chamber wall.